On Saturday, the United Nations accused Israel of killing innocent Palestinian civilians and causing widespread hardship to the population of Gaza.
Yitzhak Herzog, the Israeli cabinet secretary, responded on Sunday, saying: "Anybody who calls this operation disproportionate has no clue about the facts on the ground. We have been attacked and bombarded for months and weeks.
"With all due respect to all those who criticise us, if anything of this nature would have happened in their homeland, they would have acted much worse."
The British foreign secretary, Margaret Beckett, also said she was "deeply concerned" by the death of a young child in an Israeli airstrike in Gaza on Saturday.
Palestinian hospital officials say 44 Palestinians have died during the offensive and more than 160 have been wounded.
"Israel has a right to defend itself but must ensure that any action is proportionate and in accordance with international law," Beckett said.
Israel rejected an offer of a ceasefire made on Saturday by Ismail Haniyeh, the Palestinian prime minister, continued to launch air attacks on Gaza on Sunday.
Four Palestinians from the Al-Aqsa Martyrs Brigades faction were wounded in an air strike on Gaza City.
Israeli aircraft also fired a missile at a Palestinian car carrying fighters in the southern Gaza Strip, killing a a civilian and injuring three other people, health officials said.
The Israeli defence minister, Amir Peretz, who has been criticised for his role in the action, said the army's Gaza operation required patience and restraint.
"The army's action in the Gaza Strip creates reactions and situations that will help bring about the release of the kidnapped soldier Gilad Shalit," he said.
In Sderot, where Peretz lives, one man was hurt when two Palestinian rockets exploded in the town.
The funerals also of three members of the same Palestinian family have also taken place.
The six-year-old girl, her 20-year-old brother and their mother were killed in an Israeli air strike late on Saturday.